1. Field of the Invention
The present invention relates to an image reading apparatus, and particularly to an image reading apparatus in which an image recorded on an original to be read such as a photographic film is read based on light transmitted through the image or light reflected from the image.
2. Description of the Related Art
There has been proposed in recent years a photographic processing method in which a film image recorded on a photosensitive material such as a photographic film (hereinafter referred to merely as photographic film) is read by an image sensor ax such as a CCD, based on light transmitted through the film image or light reflected from the film image when light is irradiated on the film image, and image data obtained by the reading is subjected to image processings including various corrections, and thereafter, the image is recorded on a recording material or is displayed on a display. It should be noted that the term photographic film used here refers to a film whose negative image or positive image is visualized by development processing, after a subject has been photographed.
In an image reading apparatus for use in reading a film image in this type of photographic processing method, a diffusion box is widely used in which illumination light emitted from a light source is made into diffused light, with the objects of making the amount of light, which is irradiated on the film image, substantially uniform, and making scratches, which are formed on the film surface when the image is recorded on a recording material, difficult to see. (See Japanese Patent Application Laid-Open (JP-A) Nos. 9-114008, 8-76271, etc.)
Conventionally, when a plurality of types of photographic film are to be read by the image reading apparatus as described above, such a diffusion box has been provided in advance for each type of photographic film, and an operator chooses the diffusion box according to the type of the photographic film to be read and disposes the chosen diffusion box at a predetermined position.
In other words, since the size of a film image recorded on a photographic film varies depending on the type of photographic film, there is a need to change an illumination range according to the type of the photographic film. Thus, there is a need to pick out and use the proper diffusion box from among several diffusion boxes according to the illumination range. In this case, a structure has also been conceived of in which a common diffusion box is used that can illuminate the entire surface of the largest film image of the film images recorded on the photographic films to be read by the image reading apparatus. However, it is desirable to irradiate an amount of light which is as large as possible on a photographic film by using a low amount of energy. Therefore, from this standpoint, it is preferable to employ a structure in which a proper diffusion box is picked out for use, from among several diffusion boxes, for each type of photographic film (for each size of photographic film).
However, in the above-described technique in which a proper diffusion box is picked out and used, from among several diffusion boxes, for each type of photographic film to be read, there is a problem in that, as the operator chooses the diffusion box according to type of the photographic film to be read and disposes it at a predetermined position, a large responsibility is imposed upon the operator and he/she may choose a wrong diffusion box.